720 THE VOYAGE OF H.M.S. CHALLENGER. 



difierent armature of the first joints in the last three paii-s of pergeopods, the incision 

 in the infero-posterior angle of the first joint in the last perseopods, and by the shorter 

 and stouter first uropods. 



Acontiostoma Tcergueleni, n. sp. (PI. XXXIIL). 



Head almost covered by the first peraeon-segment and its side-plate ; the postero- 

 lateral ano-les of the first two pleon-segments well rounded, of the third more squared ; 

 these three segments a little hairy dorsally near the distal end ; the third segment 

 distally raised above the fourth, ending with a little upturned tip ; the fourth segment 

 with a deep dorsal depression, followed by an upturned process, the dorsal margin of 

 which is hairy and faces forwards. 



Eyes large, oval. 



Upper Antennw.—Yiv&i joint broad, as long as the two following and first of the 

 flagellum united, second joint broad, not long, third short, not broad ; flagellum 

 rapidly tapering, of five joints, of which the first is the longest, with a brush of very 

 long cylinders ; the following joints except the last also have cylinders ; secondary 

 flagellum of two small joints, together not equalling the first of the primary. 



Lower Antenna. — Gland-cone fairly prominent, with blunt apex, third joint very 

 short, fourth longer than fifth, with some feathered cilia on the side, fifth as long as the 

 four joints of the short, slender flagellum united. 



Upper Lip a long, triangular plate. 



Mandibles. — A prominent tooth at the uj^per part of the cutting edge ; the 

 secondary j)late of the left mandible small, deeply bifid ; spine-row not clearly made out, 

 seemingly of two or three minute spines ; no molar tubercle of any kind perceived ; 

 palp set close to the base, the first not very short joint rising from a process which gives 

 the palp a four-jointed look ; second joint with one spine near the inner margin far from 

 the apex ; third joint very nearly as long as the second, with a constriction near the 

 base, adpressed cilia on the surface, two plumose setae at apex. The secondary plate 

 (seen through the semitransparent trunk) of the left mandible is drawn in the right hand 

 figure on the Plate, the outside of the mandible being here given instead of the inside. 



Loiver Lip). — The forward lobes seem to be very slightly ciliated and not very 

 dehiscent. 



First Maxillse. — Inner plate narrowing distally, with one small seta at the apex ; 

 outer plate long, apically capped with very short spines, probably denticulate ; a minute 

 two-jointed palp on the outer margin some way below the apex. 



Second Moxillse.. — Inner plate a little shorter than the outer, each with about half-a- 

 dozen spines or setae on the apex. 



Maxillipeds. — The inner plate long, reaching beyond the second joint of the palp, 



